the mezuza is mounted on the doorpost marking the home as Jewish, it is also reminding us of our connection to our G‑d and to our masoret.

The mezuza is actually the parchment scroll withinthe case, where there is the blessings , a biblical passage declaring the oneness of G‑d it is hand writen by an expert scribe and very religious man.

The mezuzah symbolise G‑d's watching and taking care over our homes. The name of G‑d, Sha-dai, which appears on the reverse side of the parchment, mean "Guardian of the doorways of Israel."
The placing of a mezuzah on the doors of a home or office protects the inhabitants.